Blacklist usage

[baerbock]

Dear Ward,

I would really like to see a blacklist option in nordselect:

Imagine you have a list of servers which are blocked on your favorite platform and you would like to avoid their selection.

[editicalu]

This in fact seems like a nice to have feature. Due to schoolwork I don't have time at the moment. If you're familiar with Rust, you can try to implement it yourself. It shouldn't be so hard, due to the Filter-trait.